Bulb socket

Abstract: A bulb socket has a socket main body and a pair of bulb clamping pieces for holding a base of a bulb. The bulb clamping pieces have projection pieces formed by cutting out and raised up so that not only the base of the bulb is clamped by the bulb clamping pieces by resiliency, but also the edges of the clamping pieces bite into and catch leads raised and bent along the base. Alternatively, a first holding portion and a second holding portion are provided in each of clamping pieces to hold a base of the bulb by way of two-point support by the first and second holding portion of each of the clamping pieces. As a result, the bulb holding force is so increased as to reliably prevent the bulb from being detached from the bulb socket even if the bulb is located at a position susceptible to impact.

Description: BACKGROUND OF THE INVENTION The invention relates to a bulb socket that feeds power to a wedge base bulb by holding the wedge base bulb, more particularly, to an improved bulb socket that can effectively keep the bulb from being detached therefrom. A wedge base bulb and a bulb socket to which the wedge base bulb is attached are used, e.g., in a lamp of an automobile. Generally, the bulb socket has a socket main body, and inside the socket main body is a bulb holding chamber that is opened upward to allow the bulb to be accommodated therein. A pair of bulb clamping pieces having resiliency are attached to the inside of the bulb holding chamber so that the base portion of the bulb inserted into the bulb holding chamber can be clamped with resiliency and come in contact with leads extending on the base to electrically connect the bulb socket to the bulb. For, example, a bulb socket for feeding power by holding a wedge base bulb such as shown in Figure 1 has heretofore been known. That is, a bulb insertion hole 104 that allows a base portion 103a of a wedge base bulb 103 to be inserted thereinto and a connector insertion hole 105 that allows a connector (not shown) to be inserted thereinto are arranged on the upper side and on the lower side of the main body 102 of a bulb socket 101. Holding metals 106, each holding the base portion 103a of the wedge base bulb 103 and supplying power thereto, are attached to both sides of the bulb insertion hole 104 on the upper side. Each holding metal 106 has a terminal 106a at a lower portion thereof and holding pieces 106b formed by bending the bifurcated portions of the terminal 106a inward in the middle. A pair of holding portions 106c are formed by further bending the upper portions of the holding pieces 106b inward to be given resiliency for clamping the base portion 103a. To attach the wedge base bulb 103 to the thus constructed socket main body 102, the base portion 103a is inserted into the bulb insertion hole 104 and then set between the holding portions 106c. As a result, the holding portions 106c come to clamp the base portion 103a by way of single-point support at both left and right sides to allow the wedge base bulb 103 to be attached to the socket main body 102. However, such conventional structure addresses the problem that the holding strength is weak, because the base portion 103a of the wedge base bulb 103 is attached to the socket main body 102 while held by way of single-point support, i.e., only by the holding portions 106c of the holding metal 106. As a result, when a strong impact is applied to the wedge base bulb 103, the wedge base bulb 103 is likely to be detached from the socket main body 102 if the wedge base bulb is disposed at a position close to the trunk room of an automobile such as at the high mount stop lamp or the license plate lamp, because the impact applied to these lamps is strong and the strength of the socket main body 102 to hold the wedge base bulb 103 is not sufficient. In addition, although it is conceivable to improve the holding strength by increasing resiliency while using thicker special members at the holding portions, such design is disadvantageous in terms of parts cost. A conventionally taken measure to this problem is disclosed in Japanese Unexamined Utility Model Publication No. 2-47782. The main portion of the structure disclosed in the above publication is shown in Figure 2. That is, projected portions c bulge out on both upper surfaces of a base portion b of a bulb a , and resilient retaining pieces f retained by the projected portions c are formed on the inner surface of a bulb holding chamber e of a socket main body d . However, this structure is characterized as arranging the detach prevention portion (the projected portions c and the resilient retaining pieces f ) as well as electrical connection portion (the bulb clamping pieces) separately from each other. Therefore, the internal structure of the socket main body d is complicated, which in turn complicates the mold, thus elevating the cost of manufacture. In addition, a specially specified bulb a with the projected portions c provided must be prepared, which does not meet a requirement of general-purpose structure. While a bulb socket for holding a wedge base bulb as discussed before in connection with Figure 1 is known form European Patent Publication 0545316, it is furthermore known from UK-Patent Publication 2145883, to provide bulb clamping pieces inside a bulb holding chamber of a bulb socket, one of said bulb clamping pieces having a folded back portion designed for engaging a recess in a wedge base of the respective wedge base bulb, such bulb clamping piece having said folded back portion not serving for making contact to leads of the bulb provided on the base thereof. A folded back portion of a bulb clamping piece in a bulb socket known from US-Patent 5031961 has the purpose of giving support to a corresponding bulb clamping piece not making contact with electrical leads of the inserted bulb in order to equalize the clamping forces of opposed bulb clamping pieces. It is an object of the present invention to improve the clamping force in a bulb socket with the features of the preamble of claims 1 and 5, respectively, without complicating the internal structure of the respective socket main body. This object, in accordance with the present invention, is achieved by the characterizing features of claim 1 and claim 5, respectively. Thus, according to a first aspect of the invention, a bulb socket includes bulb clamping pieces attached inside a bulb holding chamber, the clamping pieces clamping a base of a bulb and being connectable to leads extending on the base, the bulb holding chamber being opened to a socket main body. Edges are formed on the bulb clamping pieces, the edges being capable of biting into the leads so that such a movement of the bulb as to allow the bulb to come off the socket main body can be prevented. Further, the edges may be distal end edges ofprojected pieces cut and raised from the bulb clamping pieces, the edges may be end edges folded back on the bulb clamping pieces. Still further, according to the second aspect of the invention, a bulb socket for hoding a wedge base bulb that includes: a holding metal being electrically connected to a terminal; a pair of holding pieces, disposed on the holding metal, for clamping a base portion and a second holding portion being disposed on each holding piece and exttending in a direction of insertion of the base portion. In such bulb socket, both the first and second holding portions have a center of swing set therebetween with respect to the holding piece, and the second holding portions disposed on a deeper side in terms of the direction of insertion of the base portion are expandable as the base portion is further inserted. According to the first aspect of the invention, when the base of the bulb is inserted into the bulb holding chamber of the socket main body, the base of the bulb is clamped by the bulb clamping pieces and, at the same time, the edges formed on the bulb clamping pieces, e.g., the end edges cut and raised as projected pieces, the end edges folded back as folded back pieces, or the opening edges formed as the window openings, bite into the leads extending on the base to prevent the base of the bulb from being detached from the socket main body. The bulb holding force is so increased as to prevent the bulb from coming off the bulb socket even if the bulb is mounted on a place subject to impact. In addition, the edges are formed only by simply machining the bulb clamping pieces. Therefore, an increase in the cost of manufacture can be minimized. Moreover, no modification or addition is necessary on the bulb side, so that the bulb socket is of general-purpose type, which can accommodate any conventional types of bulbs. According to the second aspect of the invention, when the wedge base bulb is inserted into the bulb socket, both second holding portions disposed at a deep position in terms of the insertion direction are expanded by the base portion having passed through the space between both first holding portions. Thus, the front end of the base portion in terms of the insertion direction is clamped. As a result, each holding piece swings around the center of swing between the corresponding first and second holding portions, which in turn makes the distance between both first holding portions disposed at a shallow position in terms of the insertion direction to narrow and thereby clamps the rear end of the base portion in terms of the insertion direction. That is, the swing of both holding pieces associated with the insertion of the base portion of the wedge base bulb allows both the front end side and the rear end side of the base portion in terms of the insertion direction to be clamped by the first and second holding portions. Therefore, the base portion of the wedge base bulb is supported at two points, i.e., by the first holding portions and the second holding portions, thus making the holding reliable. The base portion of the wedge base bulb is clamped by way of two-point support implemented on the front end side and on the rear end side in terms of the insertion direction in holding the wedge base bulb. Therefore, the invention can provide the excellent advantages that the bulb holding force of the bulb socket is improved and the impact resistance thereof is increased as well. In addition, the bulb socket can be formed of a sheet metal having a predetermined thickness without using expensive specially shaped members. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side sectional view showing a conventional bulb socket and a conventional wedge base bulb; Figure 2 is a diagram illustrative of a conventional bulb socket and a conventional wedge base bulb; Figure 3 is a front view showing the external appearance of a bulb socket, which is a first embodiment of the device, and of a bulb; Figure 4 is a sectional view of the bulb socket, which is the first embodiment, mounted on a mounting plate; Figure 5 is a partially enlarged front view showing a detail of a clamping portion according to the first embodiment; Figure 6 is a perspective view of a bulb clamping piece according to the first embodiment; Figure 7 is a perspective view of a bulb clamping piece according to a second embodiment; Figure 8 is a perspective view of a bulb clamping piece according to a third embodiment; Figure 9 is a perspective view of a bulb clamping piece according to a fourth embodiment; Figure 10 is a perspective view of a bulb according to a fifth embodiment; Figure 11 is a diagram illustrative of a bulb clamping piece according to the fifth embodiment; Figure 12 is a diagram illustrative of a bulb clamping piece according to a sixth embodiment. Figure 13 is a side sectional view of a bulb socket to which a wedge base bulb is attached, according to a seventh embodiment; Figure 14 is a side sectional view of the bulb socket according to a seventh embodiment; Figure 15A is a side view of a holding metal; Figure 15B is a front view of the holding metal; Figure 16A is a side view before insertion; Figure 16B is a side view at the time the wedge base bulb is half inserted into the holding metal; and Figure 16C is a side view at the time the wedge base bulb is completely inserted into the holding metal. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Embodiments of the device will now be described with reference to Figures 3 to 12. Figures 3 to 6 show a first embodiment, which exemplifies a bulb socket to which a small-sized wedge base bulb is attached. The wedge base bulb 201 has an elongated filament 3-sealed glass bulb 202, and a plate-like wedge base 204 integrally extends on the end side thereof. A longitudinally extending cylindrical portion bulges out in a central portion of the base 204, although not shown in the drawing in detail. Horizontally extending grooves 205 are formed on both front and back surfaces of the base 204 excluding the cylindrical portion. Each horizontally extending groove 205 is substantially semi-circular in section. A pair of leads extend from the bottom end surface of the base 204. One of the leads is folded back so as to extend along the front surface of the base 204, and the other is also folded back so as to extend along the back surface of the base 204, both up to such a position as to intersect the horizontally extending grooves 205, respectively. On the other hand, a socket main body 211 of the bulb socket 210 is formed into a substantially cylindrical part. A collar 212 is formed so as to project from the entire circumference in the middle of the outer surface of the socket main body 211. Inside the socket main body 211 is a partition wall 213, which stands up to a position slightly lower than the level that corresponds to the collar 212. The partition wall 213 divides the inner space of the socket main body 211 into upper and lower chambers. The upper chamber is a bulb holding chamber 215 that contains the bulb 201, and the lower chamber is a connector insertion chamber 216 into which a not shown female connector is inserted. On the bottom surface of the bulb holding chamber 215 are a pair of symmetrically confronting projected walls 219 erected. An insertion groove 218 is interposed between these projected walls 219 so that the base 204 portion can be received therein. Two terminal fittings 220 are juxtaposed inside the insertion groove 218 so as to correspond to the two extremities of the base 204 in the width direction (only one of the terminal fittings 220 is shown in Figures 4 and 5). Each of both terminal fittings 220 is composed of a pair of bulb clamping pieces 222 and a male terminal piece 221. The pair of bulb clamping pieces 222 confront each other so that the base 204 portion of the bulb 201 can be clamped from both left and right sides thereof. The male terminal piece 221 extends downward integrally from the bulb clamping pieces 222 and projects into the connector chamber 216 while passing through the partition wall 213. In addition, each terminal fitting 220 is provided with a not shown retaining means, so that the terminal fittings 220 are incorporated into the socket main body 211 so as not to be detached therefrom. Further, clamping portions 223 are formed on the upper end sides of both bulb clamping pieces 222 by bending the bulb clamping pieces 222 in gentle curves toward the horizontally extending grooves 205 of the base 204. As shown in Figure 6, what is particularly characterized is that the respective clamping portions 223 are provided with projected pieces 229. The respective projected pieces 229 have the lower end portions thereof cut and raised obliquely inward, so that the edges of the thus cut and raised lower end portions constitute edges 230. The edges 230 are abutted against the horizontally extending grooves 205 from above in an oblique direction. As a result, the edges 230 are caught by the leads 206 that go along the horizontally extending grooves 205 so as to bite into the leads 206. It should be noted that the socket main body 211 is designed to be mounted while sealed in such a manner that the bulb holding chamber 215 side of the socket main body 211 is inserted into a mounting hole 227 formed on a mounting plate 226 from the back after a gasket 224 has been set on top of the collar 212 and then with a mounting projection 228 retained by the opening edge of the mounting hole 227 while rotated by a predetermined angle, as shown in Figure 4. The mounting projection 228 projects from the outer circumference of the bulb holding chamber 215. A mode of operation and effect of the thus constructed bulb socket, which is the first embodiment of the device, will be specifically described next. When the base 204 side of the bulb 201 is inserted into the bulb holding chamber 215 of the socket main body 211, the base 204 causes the respective bulb clamping pieces 222, 222 to expand against the resiliency. As the base 204 is pushingly inserted into the insertion groove 218, the base 204 reaches the deepest end of the insertion groove 218 and the horizontally extending grooves 205 thereby correspond to the clamping portions 223 of the bulb clamping pieces 222. At that instance, with the upper end sides of the bulb clamping pieces 222 being swung inward due to the restitutive force, the clamping portion 223 of one of the pair of the bulb clamping pieces 222 is fitted into the corresponding horizontally extending groove 205 by biasing the corresponding lead 206, whereas the clamping portion 223 of the other bulb clamping piece 222 is fitted into the horizontally extending groove 205 on the back, thereby allowing the base 204 to be clamped therebetween. As shown in Figure 5 in detail, the edges 230 that are the distal ends of the projected pieces 229 arranged on the clamping portions 223 of the bulb clamping pieces 222 bite into the leads 206 from above in an oblique direction and are caught by the leads 206 so as to reliably prevent the bulb 201 from being detached from the socket main body in the upward direction. Figure 7 shows a second embodiment of the invention. The second embodiment is characterized as forming an edge 230a by extending the upper end side of a bulb clamping piece 222a upward in advance and folding back the extended portion up to the middle of the clamping portion 223 to form a folded piece 232 so that the end edge of the folded portion bites into the corresponding lead 206. Other aspects of the structure, mode of operation, and effect of the second embodiment are the same as those of the first embodiment. Figure 8 shows a third embodiment of the invention. The third embodiment is characterized as forming an edge 230b by forming a portion extended from one side edge on top of the clamping portion 223 of a bulb clamping piece 222b in advance and having the extended portion folded back on the upper half of the clamping portion 223 to form a folded piece 233 so that the lower end edge of the folded piece 233 bites into the corresponding lead 206. Other aspects of the structure, mode of operation, and effect of the third embodiment are the same as those of the first embodiment. Figure 9 shows a fourth embodiment of the invention. The fourth embodiment is characterized as forming an edge 230c by arranging a window opening 234 in the clamping portion 223 of a bulb clamping piece 222c so that only the upper edge 230c out of the opening edges of the window opening 234 bites into the corresponding lead 206. The fourth embodiment can provide the same mode of operation and effect. Figures 10 and 11 show a socket bulb, which is a fifth embodiment of the invention, to which a large-sized wedge base bulb is attached. A large-sized wedge base bulb 201a is basically the same as the small-sized wedge base bulb except that the entire front and back surfaces of the wedge base 204 to be clamped are flat. For the wedge base bulb 201a, a projected piece 229a is formed on the clamping portion 223 extended from each bulb clamping piece 222d by cutting and raising the lower end side obliquely outward as shown in Figure 11 in a manner similar to that of the first embodiment, so that the distal end of the projected piece 229a functions as an edge 230d to bite into a corresponding lead 206a. As a result, the projected pieces 229a contribute to preventing the wedge base bulb 1a from being detached from this bulb socket. Further, bulb sockets characterized as forming a folded piece on the clamping portion of each bulb clamping piece and using the end edge of the folded piece as an edge as in the second and third embodiments may also be applied to the large-sized wedge base bulb. Still further, in the bulb socket of such type that the clamping portion of each bulb clamping piece has a window opening as in the fourth embodiment, it is desirable that the upper edge of a window opening 234a is located in the most largely bulged portion of a bulb clamping piece 222e as shown in Figure 12 which is sixth embodiment, so that the upper edge of the window opening 234a serves as an edge 230e to bite into the corresponding lead 206a to prevent the bulb from being detached from the bulb socket. A seventh embodiment of the invention will now be described in detail with reference to Figures 13 to 16C. A bulb socket 110 shown in Figure 13 is designed to hold a single filament type wedge base bulb 112. The wedge base bulb 112 has a flat base portion 112c formed integrally therewith on a lower portion of a bulb portion 112b containing a filament 112a therein. Two leads extended from the lower surface of the base portion 112c are folded back toward both left and right sides of the base portion to form power supply terminals. The main body 111 of the bulb socket 110 is substantially cylindrical in structure and made of a synthetic resin material. A bulb insertion hole 114 into which the base portion 112c of the wedge base bulb 112 is inserted and a connector insertion hole 116 that allows a not shown connector for conduction to be connected thereto are opened so as to face oppositely in the vertical direction. A pair of holding metals 20 such as shown in Figures 15A and 15B are provided on the socket main body 111. These holding metals 120 serve the functions of supplying power to the wedge base bulb 112 as well as keeping the wedge base bulb 112 from being detached from the bulb main body 111. As shown in Figures 15A and 15B, each holding metal 120 is formed by bending a metal sheet made of an electrically conducting heat-resistant copper alloy, and has a terminal 122 at the lower portion thereof so as to be connected to the not shown connector. Symmetrically bifurcated support portions 124 are formed on the terminal 122. Each support portion 124 is slitted at two lateral positions and bent inward. Holding pieces 126 that are swingable with the bent portion 124a of each support portion 124 as the center of swing, are formed integrally with each support portion 124. To form the holding pieces 126, the slitted portions at the two lateral positions of each support portion 124 are also bent integrally with the holding pieces 126. First holding portions 128 that are similarly bent inward are arranged at the upper portions of the holding pieces 126. In addition, second holding portions 130 that are similarly bent are arranged at the lower portions of the holding pieces 126. The holding pieces 126 are opened apart upward with the distance between the second holding portions 130 being narrower than the distance between the first holding portions 128. It is between the first holding portion 128 and the second holding portion 130 that the bent portion 124a serving as the center of swing is located. The distance between the second holding portions 130 increases as the base portion 112c of the wedge base bulb 112 is inserted and the distance between the first holding portions 128 decreases as the holding pieces 126 are swung around the center of swing. It should be noted that a pawl piece 132 is arranged on the rear side in the middle of each holding metal 120. The pawl pieces 132 keep the wedge base bulb from being detached when the wedge base bulb is inserted into the bulb socket 110. As shown in Figure 14, the holding metals 120 are inserted into a pair of insertion grooves 134 arranged at positions at which side walls of the bulb insertion hole 114 of the socket main body 111 confront each other, and the terminal 122 projects toward the connector insertion hole 116. The holding metals 120 are undetachably locked as the pawl pieces 132 are engaged with not shown engagement portions arranged within the insertion grooves 134. When the holding metals 120 are attached to the socket main body 11 in this way, the holding pieces 126 supported by the support portions 124 are set at positions inside the bulb insertion hole 114 into which the base portion 112c of the wedge base bulb 112 is inserted. A procedure for attaching the wedge base bulb 112 to the thus constructed bulb socket 110 will be described next. As shown in Figure 16A, the base portion 112c of the wedge base bulb 112 is caused to confront both the holding pieces 126 of each holding metal 120. Then, as shown in Figure 16B, the base portion 112c is inserted into the first holding portions 128 of the holding pieces 126 of the holding metal 120. As a result, the first holding portions 128 clamp the rear side of base portion 112c in terms of the insertion direction. Since the front end of the base portion 112c in terms of the insertion direction starts to be inserted into the space between the second holding portions 130, the holding pieces 126 are swung with the bent portions 124a as the centers of swing, so that the distance between the first holding portions 128 starts decreasing. As the base portion 112c is further inserted, the front end of the base portion 112c in terms of the insertion direction enters into the space between the second holding portions 130 completely, so that the distance between the second holding portions 130 is expanded. As a result, the holding pieces 126 are swung with the bent portions 124a as the centers of swing as the distance between the second holding portions 126 is expanded, so that the distance between the first holding portions 128 is decreased, thus clamping a recessed portion 112d of the rear end of the base portion in terms of the insertion direction between the first holding portions 128. Accordingly, the base portion 112c is held more reliably by the holding pieces 126 of each holding metal 120 by way of two-point support implemented by the first holding portions 128 that are biased in such a direction as to narrow the distance therebetween and by the second holding portions 130 that are expanded. As described in the foregoing, according to the seventh embodiment, the base portion 112c of the wedge base bulb 112 is held by way of two-point support implemented by the first holding portions 128 on the upper end side of the holding pieces 126 on the one hand and by the second holding portions 130 on the lower end side of the holding pieces 126 on the other, the holding pieces 126 being arranged so as to be swingable with the bent portions 124a of the support portions 124 of each holding metal 120 as the centers of swing. Therefore, the force for holding the wedge base bulb 112 is increased, thereby making the holding reliable. It is, therefore, particularly effective to apply this embodiment to lamps mounted close to the trunk room of an automobile to which a strong impact is applied, because this embodiment can improve impact-resistance. In addition, the base portion can be held reliably by way of two-point support implemented by the first holding portions 128 and the second holding portions 130 of each holding metal 120, each of which has a certain plate thickness. Therefore, it is no longer necessary to use expensive specially shaped members to improve resiliency of the holding portions, which provides an advantage in terms of parts cost. It should be noted that while the support portions 124 of the holding metal 120 and the holding pieces 126 are made of a metal sheet integrally and are connected by the bent portions 124a, the holding metal 120 may be formed, e.g., separately from the holding pieces 126, and both may be welded together so that the welded portion may serve as the center of swing.

Claims: A bulb socket for holding a wedge base bulb (201) comprising: a main body (211) having a bulb holding chamber (215); bulb clamping pieces (222) attached inside said bulb holding chamber (215), said clamping pieces clamping a base (204) of a bulb and being connectable to leads (206, 206a) extending on said base and having formed thereon edges (230) cooperating with said base for preventing falling off of said bulb (201), characterized in that said edges have the form of biting edges for biting into said leads to prevent falling off. A bulb socket according to claim 1, wherein the edges (230) are distal end edges of projected pieces (229) cut out and raised from the bulb clamping pieces (222). A bulb socket according to claim 1, wherein the edges (230a,b) are end edges folded back (232) on the bulb clamping pieces (222a,b). A bulb socket according to claim 1, wherein the edges (230c) are edges of window openings (234) formed in the bulb clamping pieces (222c). A bulb socket (110) for holding a wedge base bulb (112) comprising: a main body (111) having a bulb holding chamber; a holding member (120) being electrically connected to a terminal (122) including a pair of holding piece members (126) for clamping a base portion of the wedge base bulb, characterized in that, each holding piece member has a first holding portion (128) and a second holding portion (130) extending in a direction of insertion of the base portion; wherein each of the first and second holding pieces has a center of swing (124a) between said first and second holding portions, and the second holding portions disposed on a deeper side in direction of insertion of the base portion are expandable as the base portion is further inserted.

Inventors: INOUE NORI, TAKANASHI HITOSHI, INOUE, NORI, TAKANASHI, HITOSHI, INOUE, NORI, C/O SUMITOMO WIRING SYSTEMS, LTD., TAKANASHI, HITOSHI, C/O SUMITOMO WIRING SYST. LTD.
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1994
Main classification: H01R33
IPC codes: H01R33